What causes obesity?
Food intake and exercise
One cause of obesity is an imbalance between what food you eat and how much movement you get.
Long daily commutes, desk jobs and communities with less green space make it more difficult to get enough exercise5.
Type of food
In our modern lives, there are more energy-dense foods available which are often higher in sugar and fat. These foods are often cheaper, easier to access and more convenient for people leading busy lives5.
Appetite signals and hormones
Chemical sensors in our blood called hormones give us a signal when we’re hungry, so we eat, and when we’re full, so we stop6.
For people who are obese, these hormones don’t work as they should, meaning you have to eat more before you feel full6. These hormones make it harder for you to lose weight and keep it off7.
Your genes
Your genes play a big role in whether you will develop obesity. Studies on twins who grew up in different homes found their genes had a bigger impact on whether they had a higher BMI8. In this study, they found environmental factors had little impact.
This may sound disheartening, but it doesn’t mean you should give up on losing weight. It just shows that obesity is not your fault.
Stress management
Stress is a natural response to challenging situations. However, long-term stress can be a problem for your health.
When you’re stressed, cortisol levels rise in your blood, which increases your appetite. When you have higher cortisol levels, you’re more likely to choose less healthy foods9 and then your body metabolises the food slower, leading to weight gain10.
Quality and quantity of sleep
How long you sleep, and the quality of your sleep can also be a risk factor of obesity11.
Studies have found people who often get less sleep than they need have hormone changes that increase their appetite, leading to weight gain12.
Doing shift work at night has also been found to be a risk factor for obesity13.
Prescription medications
Some medicines may affect your weight, particularly if you’re on them for a long time. Some medicines might make you feel hungrier, others might affect your body’s metabolism.
If you suspect your medicine is contributing to your weight gain, it’s important not to stop taking them. Talk to your doctor about what the best approach is in your situation.
Environmental factors
Where you live can have a direct impact on your weight. Advertising, access to fresh fruit and vegetables and support from your government, workplace and community can affect the food choices you make and how much exercise you’re able to do.5
For example, in rural Canada, about one in three adults are living with obesity, compared to one in four adults live with obesity in urban centers.14
In Canada overall, adult obesity is more prevalent among disadvantaged population groups such as those unemployed or with lower household income and education levels.15
